JP5353441B2 - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent generation of useless inspection and repair work based on an erroneous result of gas leakage determination in a structure attaining fuel gas leakage determination in a fuel cell system. <P>SOLUTION: The fuel cell system 10 includes a fuel cell stack 12, a step-up converter 46, a control part 40 and a current sensor. The current sensor detects a current flowing through the step-up converter 46 or between the step-up converter 46 and the fuel cell stack 12. The control part 40 includes a gas leakage determination means 74 serving as a means for determining hydrogen gas leakage in a fuel gas supply passage 22 and performing a gas leakage determining process by increasing the pressure in the fuel gas supply passage 22 to determine hydrogen gas leakage according to a later pressure fluctuation, and a short fault determination means 76 for determining generation of a short fault in the step-up converter 46 when a current sensor-detected current value or a current-time integrated value based the detected current value exceeds a threshold value in the gas leakage determining process. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention includes a fuel cell that is supplied with fuel gas from a fuel gas supply source through a fuel gas flow path and generates power by an electrochemical reaction between the fuel gas and an oxidizing gas, and a voltage converter that converts the output voltage of the fuel cell. The present invention relates to a fuel cell system provided.

  The fuel cell stack is configured by stacking a plurality of sets of fuel cell units, for example, a membrane-electrode assembly (MEA) composed of an anode side electrode, an electrolyte membrane and a cathode side electrode and a separator. That is, each fuel cell is configured by arranging an anode side electrode on one side of an electrolyte membrane made of a polymer ion exchange membrane, a cathode side electrode on the other side, and further providing separators on both sides. doing. A plurality of such fuel battery cells are stacked and sandwiched between current collector plates, insulating plates, and end plates to constitute a fuel cell stack that generates a high voltage.

  In such a fuel cell, a fuel gas, for example, a gas containing hydrogen is supplied to the anode side electrode, and an oxidizing gas, for example, air is supplied to the cathode side electrode. As a result, the fuel gas and the oxidizing gas are subjected to an electrochemical reaction to generate an electromotive force, and water is generated at the cathode side electrode.

  Conventionally, in a fuel cell system, from the viewpoint of safety, it has been considered to perform leak detection that detects whether there is a leak of fuel gas from a fuel gas flow path such as a pipe through which fuel gas flows when the system is started. It has been. For example, in a system in which hydrogen gas is supplied from a hydrogen supply source to a fuel cell through a fuel gas flow path, the hydrogen gas is supplied into the fuel gas flow path by the control unit at the time of startup. The pressure detected by the pressure sensor is monitored, and when the pressure drops below the threshold, it is determined that there is a hydrogen gas leak and an abnormality has occurred, and that the pressure is normal when the pressure is equal to or higher than the threshold. judge.

  For example, as described in Patent Document 1, a hydrogen supply source that supplies hydrogen to the fuel cell, a fuel supply channel that is provided between the hydrogen supply source and the hydrogen supply port of the fuel cell, and a fuel supply channel There is known a fuel cell system including a shut-off valve provided in the valve, a hydrogen pressure regulating valve provided on the downstream side of the shut-off valve, a pressure sensor for detecting a hydrogen gas pressure in a fuel supply path, and a control unit. When performing the pressurization process of the fuel supply path at the time of starting the system, the control unit is configured such that the pressurization value of the fuel supply path downstream from the shutoff valve is equal to or lower than the pressure control value of the upstream hydrogen pressure control valve. The open / close state of the shut-off valve is controlled so that it becomes a value equal to or higher than the pressure adjustment value of the hydrogen pressure control valve on the side, the pressure is detected at a predetermined cycle by the pressure sensor, and the pressure change amount or the pressure change rate after the lapse of the predetermined time When it is equal to or greater than a predetermined leak determination threshold, it is determined that a gas leak has occurred in the fuel system piping downstream of the shutoff valve.

JP 2007-134200 A

  In this way, in a fuel cell system that detects hydrogen gas leakage, there is a possibility of erroneous determination that hydrogen gas leakage is erroneously determined even though there is no abnormality in the fuel gas flow path such as piping. I understood. As a cause, the present inventor has connected a boost converter, which is a voltage converter, to the fuel cell, and when the voltage output from the fuel cell is converted by the boost converter, an abnormality occurs in the boost converter. If so, it was thought that there was a possibility of misjudgment of hydrogen gas leak. That is, with this configuration, when a short-circuit failure occurs due to contact between multiple bus bars arranged in a non-contact manner in the circuit of the boost converter or damage to the elements, the hydrogen gas leak determination is performed. When supplying hydrogen gas to the fuel cell, current may be generated due to the reaction between the hydrogen gas and the oxidizing gas when the hydrogen gas is supplied, and the hydrogen gas may be consumed, leading to a pressure drop in the fuel gas flow path. There is. In the conventional system, when a pressure drop occurs due to such a cause, it is a failure mode of short circuit of the boost converter, and there is hydrogen gas leakage even though the fuel gas flow path is normal There is a possibility of misjudgment. In this case, there is a possibility that useless inspection / repair work for the fuel gas flow path may occur based on an erroneous gas leak determination result. For example, an operator may mistakenly replace a normal part.

  An object of the present invention is to useless inspection based on an erroneous gas leak judgment result in a configuration in which fuel gas leak judgment can be performed by pressurizing the inside of a fuel gas flow path and monitoring subsequent pressure fluctuations in a fuel cell system. It is to prevent repair work from occurring.

The fuel cell system of the present invention includes a fuel cell in which fuel gas is supplied from a fuel gas supply source through a fuel gas flow path and generates power by an electrochemical reaction between the fuel gas and an oxidizing gas, and a voltage for converting the output voltage of the fuel cell. A fuel cell system comprising a conversion device, and gas leakage determination means for determining fuel gas leakage in the fuel gas flow path at the time of startup of the fuel cell system, the pressure in the fuel gas flow path being increased A gas leakage determination means for performing a gas leakage determination process for determining a fuel gas leakage according to a subsequent pressure fluctuation, and a current for detecting a current flowing between the fuel cell and the voltage conversion device, or a current flowing through the voltage conversion device The short circuit of the voltage conversion device when the detection means and the current time integrated value based on the detection current value or the detection current value of the current detection means during the gas leak determination process are equal to or greater than the threshold value And impaired determining short-circuit failure judging means to have occurred, short-circuit failure if the short-circuit fault of the voltage conversion device is determined to have occurred by determining means, short-circuit failure during processing to stop the output of the determination result of the gas leak judgment means A fuel cell system.

According to the fuel cell system of the present invention, when the fuel cell system is started up, the fuel gas leakage can be determined by pressurizing the fuel gas flow path and monitoring subsequent pressure fluctuations by the gas leakage determination means. In addition, the short circuit failure determination means causes a short circuit failure of the voltage conversion device when the detected current value of the current detection means or the current time integrated value based on the detected current value is greater than or equal to the threshold during the gas leakage determination process. since it is determined that, to prevent a short circuit by stopping the output of the determination result gas leak judgment means if a failure is determined to have occurred, wasteful inspection and repair work is generated based on erroneous gas leakage judgment result it can.

Further, the fuel cell system according to the present invention includes a fuel cell that is supplied with fuel gas from a fuel gas supply source through a fuel gas flow path, generates power by an electrochemical reaction between the fuel gas and an oxidizing gas, and an output voltage of the fuel cell. A fuel cell system comprising a voltage conversion device for converting gas pressure determining means for determining fuel gas leakage in the fuel gas flow path when starting the fuel cell system, wherein the pressure in the fuel gas flow path The gas leakage determination means for performing the gas leakage determination processing for determining the fuel gas leakage according to the subsequent pressure fluctuation and the current flowing between the fuel cell and the voltage conversion device, or the current flowing through the voltage conversion device Voltage detection when the current detection means to detect and the current time integrated value based on the detected current value or the detected current value of the current detection means during the gas leak determination process is equal to or greater than the threshold value Further comprising a short-circuit failure judging means determines that short-circuit failure of location occurs, when a short-circuit failure of the voltage conversion device is determined to have occurred by short-circuit failure judging means, and notification means for notifying the occurrence of short-circuit failure This is a fuel cell system.

According to the above configuration, when the fuel cell system is started up, the fuel gas leakage can be determined by pressurizing the fuel gas flow path and monitoring subsequent pressure fluctuations. In addition, the driver of a fuel cell system or a vehicle equipped with a fuel cell system can recognize the occurrence of a short-circuit fault in the voltage converter and prevent unnecessary inspection and repair work from occurring based on the erroneous gas leak judgment result. it can.

  Moreover, the fuel cell system according to the present invention preferably includes an operation stop unit that stops the power generation operation of the fuel cell when the short circuit failure determination unit determines that a short circuit failure has occurred in the voltage converter.

  According to the above configuration, since the power generation operation of the fuel cell can be automatically stopped when a short circuit failure occurs in the voltage conversion device, an unstable operation of a load connected to the fuel cell via the voltage conversion device can be prevented.

  According to the fuel cell system of the present invention, in a configuration in which fuel gas leakage determination can be performed by pressurizing the inside of the fuel gas flow path and monitoring subsequent pressure fluctuations, useless inspection based on erroneous gas leakage determination results The occurrence of repair work can be suppressed.

It is a figure which shows the basic composition of the fuel cell system of an example of embodiment of this invention. FIG. 2 is a diagram showing an electric circuit for driving a travel motor as a load by the fuel cell stack in the system of FIG. 1. FIG. 2 is a schematic diagram showing a state in which no current is generated by a current sensor provided in the boost converter when the boost converter is normal in the system of FIG. 1. In the system of FIG. 1, it is the schematic which shows a mode that there exists an electric current generation | occurrence | production with the current sensor provided in the boost converter at the time of the circuit short circuit of a boost converter. When the gas leak determination is executed using the system of FIG. 1, the upper half is a diagram showing an example of the temporal change in the hydrogen pressure in the fuel gas flow path, and the lower half is the current sensor portion. It is a figure which shows one example of the time change of the electric current which flows through. It is a figure which shows the main flow of the flowchart which shows the control method at the time of starting which performs short circuit determination with a gas leak determination using the system of FIG. It is a figure which shows the subroutine performed with the main flow of FIG.

  Hereinafter, an example of an embodiment according to the present invention will be described in detail with reference to the drawings. 1 to 7 show an example of an embodiment of the present invention. As shown in FIG. 1, the fuel cell system 10 is used by being mounted on a fuel cell vehicle, for example, and includes a fuel cell stack 12. The fuel cell stack 12 has a plurality of fuel cells stacked, and a current collector plate and an end plate are provided at both ends of the fuel cell stack 12 in the stacking direction. Then, the plurality of fuel cells, the current collector plate, and the end plate are fastened with tie rods, nuts, and the like. An insulating plate can also be provided between the current collector plate and the end plate.

  Although a detailed view of each fuel cell is omitted, it is assumed that, for example, a membrane assembly in which an electrolyte membrane is sandwiched between an anode side electrode and a cathode side electrode and separators on both sides thereof are provided. Further, hydrogen gas that is a fuel gas can be supplied to the anode side electrode (hereinafter simply referred to as “anode”), and air that is an oxidizing gas is supplied to the cathode side electrode (hereinafter simply referred to as “cathode”). It is possible. Then, hydrogen ions generated by the catalytic reaction at the anode, that is, protons are moved to the cathode through the electrolyte membrane, and water is generated by causing an electrochemical reaction with oxygen at the cathode. In addition, an electromotive force is generated by moving electrons from the anode to the cathode through an external electric circuit. That is, the fuel cell stack 12 in which a plurality of fuel cells shown in FIG. 1 are stacked generates power by an electrochemical reaction between the oxidizing gas and the fuel gas.

  In order to supply air, which is an oxidizing gas, to the fuel cell stack 12, an oxidizing gas supply channel 14 is provided. In order to discharge air off-gas which is air after being subjected to an electrochemical reaction from the fuel cell stack 12, an oxidizing gas system discharge flow path 16 is provided. An air compressor 18 serving as an oxidizing gas supply unit is provided upstream of the oxidizing gas supply channel 14. The air pressurized by the air compressor 18 is humidified by the humidifier 20 and then supplied to the oxidizing gas flow path on the cathode side of the fuel cell stack 12. The air off-gas supplied to the fuel cell stack 12 and subjected to an electrochemical reaction in each fuel cell is discharged from the fuel cell stack 12 through the oxidizing gas system discharge flow path 16 and then passes through the humidifier 20. Then released into the atmosphere. The humidifier 20 serves to humidify the moisture obtained from the air off-gas discharged from the fuel cell stack 12 to the air before being supplied to the fuel cell stack 12.

  On the other hand, a fuel gas supply channel 22, which is a fuel gas channel, is provided to supply hydrogen gas, which is a fuel gas, to the fuel cell stack 12. A fuel gas supply source 24 such as a high-pressure hydrogen tank is provided upstream of the fuel gas supply flow path 22. The fuel gas supply channel 22 is provided with an open / close valve 26 that is an electromagnetic valve for blocking or connecting between the channel 22 and the fuel gas supply source 24. Hydrogen gas is supplied from the fuel gas supply source 24 to the fuel cell stack 12 via the on-off valve 26. In addition, a fuel gas system discharge passage 28 is provided to discharge hydrogen off-gas, which is hydrogen after being subjected to an electrochemical reaction, from the fuel cell stack 12. The hydrogen off gas includes unreacted hydrogen.

  The hydrogen off-gas that has been supplied to the fuel gas passage on the anode side of the fuel cell stack 12 and subjected to the electrochemical reaction is discharged from the fuel cell stack 12 through the fuel gas discharge passage 28. A fuel gas recirculation path 32 is connected to the fuel gas system discharge flow path 28 via a gas-liquid separator 30. The fuel gas recirculation path 32 is provided to return the hydrogen off-gas containing unreacted hydrogen gas discharged from the fuel cell stack 12 to the fuel gas supply path 22. Further, a hydrogen pump 34 that is a fuel gas circulation pump is provided in the fuel gas recirculation path 32. The hydrogen pump 34 returns the hydrogen off gas to the fuel gas supply flow path 22 through the fuel gas recirculation path 32, merges with the new hydrogen gas sent from the fuel gas supply source 24, and then supplies the hydrogen off gas to the fuel cell stack 12 again. . The hydrogen pump 34 is connected to the secondary battery 36 and is driven by power supplied from the secondary battery 36. Further, the fuel cell system 10 is provided with a pressure sensor 38 which is a pressure detecting means for detecting the pressure of the fuel gas supply flow path 22. A detection signal of the pressure sensor 38 is input to the control unit 40.

  The hydrogen off-gas discharged from the fuel cell stack 12 is sent to the fuel gas recirculation path 32 after moisture is removed by the gas-liquid separator 30. An exhaust / drain channel 42 is connected to the gas-liquid separator 30, and an exhaust / drain valve and a purge valve 44 that is an electromagnetic valve are provided in the middle of the exhaust / drain channel 42. By operating the purge valve 44 according to a command from the control unit 40, moisture and hydrogen off-gas are discharged to the outside. By performing this discharge operation intermittently, it is possible to prevent a decrease in the voltage of the fuel cell due to an increase in the impurity concentration in the hydrogen off-gas. Note that the exhaust passage provided with the purge valve can be connected to a portion of the fuel gas discharge passage 28 away from the gas-liquid separator 30.

  The output voltage from the fuel cell stack 12 is converted so as to be boosted by a boost converter 46 that is a voltage converter, and then output to the motor 48 that is a load. For this purpose, the fuel cell system 10 includes a boost converter 46, an inverter 50, a motor 48, and a secondary battery 36. The fuel cell stack 12, the boost converter 46, the inverter 50, and the motor 48 constitute a motor drive circuit 52 that is an electric circuit. For example, when the fuel cell system 10 is mounted on a fuel cell vehicle and used, the motor 48 is used as a traveling motor that is a drive source for driving the vehicle.

  The secondary battery 36 has a voltage of 12 V, for example, and when the motor 48 is driven in a state where the fuel cell stack 12 is stopped, the output voltage from the secondary battery 36 is boosted by the boost converter 46. It can also be supplied to the motor 48 via the inverter 50. Thus, the motor 48 can be driven by the secondary battery 36 even when the operation of the fuel cell stack 12 is stopped. For example, when a switch (not shown) is provided between the secondary battery 36 and the boost converter 46, the switch is turned off when the fuel cell stack 12 is operated, and the motor 48 is driven when the fuel cell stack 12 is stopped. Control is performed by the control unit 40 to turn on this switch.

  FIG. 2 shows the motor drive circuit 52 in detail. A boost converter 46 is connected between the fuel cell stack 12 and the motor 48. In FIG. 2, the illustration of the inverter 50 (FIG. 1) is omitted. Boost converter 46 is connected to first capacitor 54 and second capacitor 56 connected in parallel between positive electrode side bus La and negative electrode side bus Lb, and to first capacitor 54 and second capacitor 56 of positive electrode bus La. And a first switching element 60 connected between a node N1 closer to the motor 48 than the reactor 58 of the positive electrode bus La and a node N2 of the negative electrode bus. The first switching element 60 is, for example, a transistor or an IGBT. A diode is connected to the first switching element 60 in parallel. The first capacitor 54 is connected to the positive electrode bus La and the negative electrode bus Lb at nodes N3 and N4. The control unit 40 shown in FIG. 1 controls the on / off switching of the first switching element 60, whereby the output voltage of the fuel cell stack 12 is boosted to a desired magnitude and output to the motor 48 side.

  A first diode 62 and a third capacitor 64 are connected in series between a node N5 between the reactor 58 of the positive electrode bus La and the node N1 and a node N6 of the negative electrode bus Lb. Further, between the node N7 between the node N3 and the reactor 58, and the midpoint between the first diode 62 and the third capacitor 64, a second switching element 66, a second diode 68, and a second reactor 70 are provided. Are connected in series. The second switching element 66 is, for example, a transistor or an IGBT. A second parallel diode is connected in parallel to the second switching element 66. The portion including the second switching element 66, the first and second diodes 62 and 68, and the second reactor 70 has a soft switching function for efficiently performing the boosting operation by the boosting converter 46. Similarly to the first switching element 60, the on / off switching of the second switching element 66 is also controlled by the control unit 40 (FIG. 1). Further, the third diode 71 is connected to the motor 48 side of the positive bus La from the node N1.

  Further, a current sensor 72 as current detection means is provided between the node N3 and the node N7 of the positive electrode bus La. The arrangement position of the current sensor 72 is not limited to the illustrated position. For example, it can be provided on the negative electrode bus Lb. A current sensor 72 can also be provided between the fuel cell stack 12 and the boost converter 46.

  The control unit 40 shown in FIG. 1 includes various signals such as a signal indicating a load request such as an accelerator opening signal of a vehicle, a pressure sensor for detecting a state in the fuel cell stack 12 and a flow path, and a temperature sensor. It has a function of acquiring a signal representing detection information, controlling the boost converter 46 and the inverter 50, and controlling the operating state of the motor 48. The control unit 40 includes a microcomputer having a CPU, a memory, and the like.

  The control unit 40 controls the driving state of the hydrogen pump 34 and the air compressor 18 and the opening / closing state of the on-off valve 26 during the power generation operation of the fuel cell stack 12. The control unit 40 includes a gas leak determination unit 74, a short circuit failure determination unit 76, a short circuit failure processing unit 78, a notification unit 80, and an operation stop unit 82.

  The gas leakage determination means 74 has a function of determining hydrogen gas leakage in a fuel gas flow channel such as the fuel gas supply flow channel 22 when the fuel cell system 10 is started. Further, the gas leak determination means 74 increases the pressure in the fuel gas supply flow path 22 by supplying hydrogen gas from the fuel gas supply source 24 to the fuel gas supply flow path 22 at the time of start-up, and causes the subsequent pressure fluctuation. Accordingly, a gas leak determination process for determining hydrogen gas leak is performed. That is, at the start of the gas leak determination process, the gas leak determination means 74 pressurizes the fuel gas supply flow path 22 by opening the on-off valve 26. When the detected pressure detected by the pressure sensor 38 reaches a preset first threshold value or more, the on-off valve 26 is closed and the subsequent detected pressure of the pressure sensor 38 is monitored. If the detected pressure falls below the second threshold value for gas leak judgment set in advance between the closing time of the on-off valve 26 and the end of the preset gas leak detection period, it is determined that there is a gas leak, When it does not fall below the threshold value, it is determined that there is no gas leak and is normal. When it is determined that there is a gas leak, the control unit 40 stops the operation of the fuel cell stack 12, for example, and displays the gas leak on a display around the driver's seat of the vehicle or a display unit such as a warning light. The determination result is output to the corresponding device. On the other hand, when a determination result indicating no gas leakage is obtained, the fuel cell stack 12 shifts to a normal power generation operation.

  Further, the short circuit failure determination means 76 is a step-up converter when the current time integrated value A based on the detected current value of the current sensor 72 during the gas leakage determination process is equal to or greater than a preset threshold value X (A ≧ X). It has a function of determining that 46 short-circuit faults have occurred. This will be described with reference to FIGS. 3 and 4 show the boost converter 46 connected to the fuel cell stack 12. In the following description, the same elements as those illustrated in FIGS. 1 and 2 are denoted by the same reference numerals. FIG. 3 shows a normal time when there is no circuit short circuit in the boost converter 46, and FIG. 4 shows an abnormal time when a circuit short circuit occurs in the boost converter 46. At the time of gas leak determination at the time of starting the system, the inside of the fuel gas supply passage 22 is added by the gas leak determination means 74 with the first and second switching elements 60 and 66 (see FIG. 2 for 66) turned off. Press. In this case, the boost converter 46 does not perform a boost operation, and no current is generated in the current sensor 72. For example, the voltage of the fuel cell stack 12 is set to 300V, and the driving voltage of the motor 48 is set to a voltage higher than the voltage of the fuel cell stack 12 such as 600V.

  On the other hand, as indicated by a thick line α in FIG. 4, if a short circuit occurs in a part of the circuit of the boost converter 46 due to some cause such as breakage of the first switching element 60, the first and second switching elements Since the circuit is short-circuited even though the switches 60 and 66 are not switched from OFF to ON, a current flowing in the direction of the arrow β in FIG. 4 is generated, and a current is generated in the current sensor 72. When the current is generated in this way, the hydrogen gas is consumed together with the oxidizing gas in the fuel cell stack 12, and the pressure in the fuel gas supply flow path 22 decreases. Further, the short circuit of the boost converter 46 is not limited to the damage of the first switching element 60. For example, referring back to FIG. 2, the midpoint of the second switching element 66 and the second diode 68 and the negative bus Lb. There is a possibility that a circuit short circuit may occur by connecting a portion indicated by a broken line γ between the node N4 and the node N6 by a short circuit of the bus bar or the like. In any case, if the pressure in the fuel gas supply flow path 22 decreases during the gas leak determination process due to such a cause, it may be erroneously determined that there is a hydrogen gas leak even though there is no hydrogen gas leak. There is sex.

  In this embodiment, in order to prevent useless inspection / repair work based on erroneous determination even in such a case, a short-circuit failure determination means 76 is provided. The short circuit failure determination means 76 calculates the current time integrated value based on the current detection value acquired from the current sensor 72 during the gas leak determination process, and the current time integrated value A during the gas leak determination process is preset. It is determined whether or not the threshold value is X or more. The “current time integrated value” refers to a value obtained by obtaining a time change curve of current from the relationship between the detected current detected at predetermined time intervals and time and integrating the time based on the time change curve. If the current time integrated value A is equal to or greater than the threshold value X (A ≧ X), the short circuit failure determination means 76 determines that a short circuit failure has occurred. On the other hand, even when the gas leakage determination process is completed, if the current time integrated value A is less than the threshold value X (A <X), the short circuit failure determination unit 76 determines that no short circuit failure has occurred.

  FIG. 5 shows the pressure in the fuel gas supply flow path 22 and the current sensor 72 portion when the hydrogen gas leakage determination and the short circuit failure determination are performed before the shift to the normal power generation operation control when the fuel cell system 10 is started. It is a figure which shows one example of a time change with the electric current which flows through. The solid line in the upper half of FIG. 5 and the lower half of FIG. 5 represent the case where the portion indicated by the broken line γ in FIG. In this case, when gas is supplied to the fuel gas supply flow path 22 by the gas leak determination means 74 and the pressure in the flow path 22 is increased, the pressure in the fuel gas supply flow path 22 detected by the pressure sensor 38 at time t1. Pressure increases gradually. Thereafter, a current is generated at time t2 and gradually increases. This is because a current is generated in the boost converter 46 due to the reaction between hydrogen gas and air in a state where the circuit of the boost converter 46 is short-circuited. Next, at time t3 when the pressure in the fuel gas supply flow path 22 reaches the first threshold value P1, the gas leak determination means 74 closes the on-off valve 26. Then, the pressure Pa in the fuel gas supply flow path 22 is equal to or lower than the second threshold value P2 set in advance when the gas leak determination means 74 reaches time t4, which is the end of the gas leak detection period ( If it is determined that Pa ≦ P2), it is usually determined that gas leakage has occurred. On the other hand, in the upper half of FIG. 5, the alternate long and short dash line δ represents the normal time when both the fuel gas supply channel 22 and the boost converter 46 are normal. In this case, even at time t4, the pressure in the fuel gas supply channel 22 does not become the second threshold value P2 or less, and it is determined that no gas leakage has occurred.

  On the other hand, in the present embodiment, the current-time integrated value based on the detected current during the gas leak determination process from time t1 to time t4 by the short-circuit failure determination means 76, that is, FIG. Calculate the time integrated value of the lower half curve. When the short-circuit fault determination unit 76 determines that the current time integrated value A is equal to or greater than the preset threshold value X (A ≧ X), it is determined that a short-circuit fault has occurred in the boost converter 46. When it is determined that a short-circuit failure has occurred, the short-circuit failure processing unit 78 outputs the determination result of the gas leak determination unit 74 to a device corresponding to the determination result, for example, a display unit that displays the gas leak determination result. Cancel. In addition, when it is determined that a short circuit failure has occurred, the notification unit 80 displays and notifies the occurrence of the short circuit failure on a display unit such as a display or a warning light. Further, the operation stopping unit 82 stops the power generation operation of the fuel cell stack 12 when it is determined that a short circuit failure has occurred. In FIG. 5, the gas leak determination is performed from the time when the pressure in the fuel gas supply flow path 22 reaches the first threshold value P <b> 1, but P <b> 1 is reached in consideration of the time during which the gas detection value is stabilized. It is also possible to make a gas leak determination after a predetermined period from the time.

  FIG. 6 and FIG. 7 are flowcharts for explaining a control method when such hydrogen gas leakage determination and short circuit failure determination are performed. For example, it is assumed that the control unit 40 includes a plurality of CPUs including a first CPU and a second CPU that are two arithmetic units. The main flow shown in FIG. 6 is executed by the first CPU, and the subroutine shown in FIG. 7 is executed by the second CPU. In this case, the gas leakage determining means 74 is constituted by the first CPU, and the short circuit failure judging means 76 is constituted by the second CPU. The flowcharts shown in FIGS. 6 and 7 are executed in parallel. 7 is started when the second CPU acquires a subroutine start signal as a start timing from the first CPU when the main flow of FIG. 6 is executed. Further, the second CPU acquires a subroutine stop signal as a stop timing from the first CPU, and if the calculated current time integrated value is not less than or equal to the threshold value, the execution ends.

  First, as shown in FIG. 6, when the fuel cell system 10 is started in step S10 in response to turning on of a start switch (not shown), the main flow is executed by the first CPU, and the fuel gas supply passage 22 is opened and closed in step S12. By opening the valve 26, pressurization in the flow path 22 is started. Then, the first CPU outputs a subroutine start signal to the second CPU (step S14), and execution of the subroutine of FIG. Next, when pressurization is completed at time t3 in FIG. 5 (step S16), gas leak detection is started by the gas leak determination means 74 (step S18), and gas leak is detected at time t4 when the gas leak detection period ends. The detection is completed, and the presence or absence of gas leakage is determined (step S20). Then, the first CPU outputs a subroutine stop signal to the second CPU (step S22). Next, in step S22, it is determined whether or not a circuit short circuit signal has been acquired from the second CPU. If it is determined that the circuit has been acquired, in step S24, the short circuit failure processing unit 78 causes the gas leakage determination unit 74 to perform gas leakage. Stops outputting the judgment result and ends. On the other hand, if it is determined in step S22 that the circuit short circuit signal has not been acquired, a signal indicating that the process proceeds to normal gas leak determination post-processing is output, and the gas of the control unit 40 that has acquired the signal is output. The leak determination post-processing means executes the process and ends the gas leak determination process. For example, when it is determined that a gas leak has occurred, the gas leak determination post-processing means stops the power generation operation of the fuel cell stack 12, and notifies the occurrence of the gas leak by a display unit such as a display or a warning light. . On the other hand, when it is determined that there is no gas leakage, the routine proceeds to normal power generation operation processing of the fuel cell stack 12.

  On the other hand, as shown in FIG. 7, when it is determined that the second CPU has acquired a subroutine start signal from the first CPU in step S30, execution of the subroutine is started. In step S32, it is determined whether or not a subroutine stop signal has been acquired from the first CPU. If not acquired, a detected current corresponding to the time from the current sensor 72 is acquired in step S34. A current time integrated value A based on the detected current is calculated. Next, in step S36, it is determined whether or not the current time integrated value A is greater than or equal to the threshold value X. If not, the process from step S32 to S36 is repeated. If it is determined in step S36 that the current time integrated value A is equal to or greater than the threshold value X, a circuit short circuit of the boost converter 46 is determined in step S38, a circuit short signal is output to the first CPU in step S40, and notification means A circuit short circuit notification signal is output to 80 and a fuel cell stop signal is output to the operation stop means 82. When the notification unit 80 acquires the circuit short circuit notification signal, the display unit such as a display notifies the driver of the fuel cell system 10 of the occurrence of a short circuit failure. When the operation stop means 82 acquires the fuel cell stop signal, the power generation operation of the fuel cell stack 12 is stopped.

  On the other hand, if it is determined in step S32 that the subroutine stop signal has been acquired, it is determined in step S42 whether or not the current time integrated value A is equal to or greater than the threshold value X, and if not greater than the threshold value X, as in step S36. In this case, the short-circuit fault determination process is terminated. On the other hand, if it is determined in step S42 that the current-time integrated value A is greater than or equal to the threshold value X, the process proceeds to step S38 and the process of step S40 is performed as described above.

  According to the above fuel cell system, the gas leak determination means 74 can determine the hydrogen gas leak by pressurizing the fuel gas supply passage 22 and monitoring subsequent pressure fluctuations when the fuel cell system 10 is started. . Moreover, the short-circuit fault determination means 76 determines that a short-circuit fault has occurred in the boost converter 46 when the current time integrated value A based on the current detected by the current sensor 72 during the gas leak determination process is equal to or greater than the threshold value X. Therefore, it is possible to prevent unnecessary inspection / repair work from occurring based on an erroneous gas leak determination result, for example, by stopping output of the determination result of the gas leak determination means 74 when it is determined that a short circuit failure has occurred.

  Further, according to the fuel cell system of the present embodiment, when the short circuit failure determination unit 76 determines that a short circuit failure of the boost converter 46 has occurred, the notification unit 80 that notifies the occurrence of the short circuit failure is provided. For this reason, the driver of the fuel cell system or the vehicle equipped with the fuel cell system can recognize the occurrence of the short-circuit failure of the boost converter 46, and wasteful inspection and repair work is generated based on the erroneous gas leak determination result. This can be prevented more effectively.

  Further, according to the present embodiment, the operation stop means 82 for stopping the power generation operation of the fuel cell stack 12 when the short circuit failure determination means 76 determines that a short circuit failure of the boost converter 46 has occurred. For this reason, since the power generation operation of the fuel cell stack 12 can be automatically stopped when a short circuit failure occurs in the boost converter 46, an unstable operation of the motor 48 connected to the fuel cell stack 12 via the boost converter 46 can be prevented. When the motor 48 is driven after the operation of the fuel cell stack 12 is stopped, for example, the controller 40 is connected between the secondary battery 36 and the boost converter 46 so that the power of the secondary battery 36 is supplied to the motor 48. Switch the selected switch from off to on.

  In the present embodiment, the short-circuit fault determination unit 76 determines whether the boost converter 46 has the current value accumulated value A based on the detected current value of the current sensor 72 during the gas leakage determination process is equal to or greater than the threshold value X. It has a function to determine that a short circuit failure has occurred. However, the present embodiment is not limited to such a configuration, and the magnitude of the detected current value itself of the current sensor 72 during the gas leakage determination process is set in advance by the short circuit failure determination means 76. It can also be configured to have a function of determining that a short circuit fault has occurred in the boost converter 46 when the threshold current value is exceeded. In this case, the short-circuit fault determination means 76 determines that a short-circuit fault has occurred in the boost converter 46 when it is determined that the detected current itself is equal to or greater than the threshold current value without calculating the current accumulated value. Even at the end of the gas leakage determination process, if the detected current is less than the threshold current value, it is determined that no short circuit failure has occurred. In this case, for example, the time integration calculation process of the current in step S34 is omitted in the subroutine shown in FIG. 7, and it is determined in step S36 whether the detected current is greater than or equal to the threshold current value, and is determined to be less than the threshold current value. If it has been determined, the process returns to step S32, and if it is determined that the value is greater than or equal to the threshold current value, the process proceeds to step S38.

  In the figure showing the time change of the current flowing through the current sensor 72 in the lower half of FIG. 5, the detected value of the current sensor 72 is a positive value that is also when the switching elements 60 and 66 are off, that is, the upper side. In addition, when there is an offset by a certain amount, the current time integrated value also increases corresponding to the offset amount. However, in this case, a highly reliable short-circuit fault determination can be performed by performing a learning process for returning the offset to the origin when calculating the current-time integrated value. In addition, when an abnormality occurs in the current sensor 72 or the pressure sensor 38, if a sensor abnormality determination unit (sensor diagnosis) (not shown) that determines the normal abnormality of each sensor 72, 38 detects an abnormal value, the detected value of the sensor is invalidated. Or by performing a process of notifying a sensor abnormality, it is possible to perform a reliable short-circuit fault determination.

  As another example of the present embodiment, in the present embodiment, when the circuit short circuit of the boost converter 46 is determined in step S38 of the subroutine of FIG. 7, without outputting the circuit short circuit signal in step S40, A short circuit notification signal can also be output to the notification means 80. In this case, in the main flow of FIG. 6, there is a possibility that the occurrence of gas leakage may be reported in spite of the short circuit failure of the boost converter 46 in the post-processing for determining gas leakage. However, since the notification means 80 notifies the occurrence of a short circuit, the driver can recognize the occurrence of a short circuit failure in the boost converter 46, and a wasteful inspection and repair work is generated based on an erroneous gas leak determination result. Can be prevented.

  Note that the booster converter 46 for the secondary battery 36 and the booster converter 46 for the fuel cell stack 12 may be provided separately without sharing the boost converter 46 between the secondary battery 36 and the fuel cell stack 12. In this embodiment, the pressure sensor 38 for detecting the pressure of the fuel gas supply flow path 22 is provided and the detected pressure of the pressure sensor 38 is monitored during the gas leak determination process. It is also possible to provide a pressure sensor such as 28 for detecting the pressure of another gas flow path, and to monitor the detected pressure of the pressure sensor 38 during the gas leak determination process.

  The circuit configuration of the boost converter and the configuration itself for supplying and discharging the gas to the fuel cell are not limited to the present embodiment, and various configurations can be adopted within the scope of the present invention.

  DESCRIPTION OF SYMBOLS 10 Fuel cell system, 12 Fuel cell stack, 14 Oxidation gas supply flow path, 16 Oxidation gas system discharge flow path, 18 Air compressor, 20 Humidifier, 22 Fuel gas supply flow path, 24 Fuel gas supply source, 26 On-off valve, 28 Fuel gas system discharge channel, 30 Gas-liquid separator, 32 Fuel gas recirculation channel, 34 Hydrogen pump, 36 Secondary battery, 38 Pressure sensor, 40 Control unit, 42 Exhaust drain channel, 44 Purge valve, 46 Boost converter , 48 motor, 50 inverter, 52 motor drive circuit, 54 first capacitor, 56 second capacitor, 58 reactor, 60 first switching element, 62 first diode, 64 third capacitor, 66 second switching element, 68 second Diode, 70 Third diode, 71 Third diode, 72 Current sensor, 7 Gas leak judgment means, 76 short-circuit failure judging means, 78 short-circuit failure during processing unit, 80 notification unit, 82 operation stop means.

Claims (3)

A fuel cell system comprising a fuel cell that is supplied with fuel gas from a fuel gas supply source through a fuel gas flow path and that generates electric power by an electrochemical reaction between the fuel gas and an oxidizing gas, and a voltage converter that converts the output voltage of the fuel cell Because
Gas leakage determination means for determining fuel gas leakage in the fuel gas flow path when starting the fuel cell system, increasing the pressure in the fuel gas flow path and reducing the fuel gas leakage in response to subsequent pressure fluctuations. A gas leak judging means for performing a gas leak judging process for judging;
Current detection means for detecting a current flowing between the fuel cell and the voltage converter, or a current flowing through the voltage converter;
A short-circuit fault determination unit that determines that a short-circuit fault has occurred in the voltage converter when the detected current value of the current detection unit or the current-time integrated value based on the detected current value is greater than or equal to a threshold value during the gas leakage determination process; ,
A fuel cell system comprising : a short-circuit fault processing unit that stops outputting the determination result of the gas leak determination unit when the short-circuit fault determination unit determines that a short-circuit fault has occurred in the voltage converter . A fuel cell system comprising a fuel cell that is supplied with fuel gas from a fuel gas supply source through a fuel gas flow path and that generates electric power by an electrochemical reaction between the fuel gas and an oxidizing gas, and a voltage converter that converts the output voltage of the fuel cell Because
Gas leakage determination means for determining fuel gas leakage in the fuel gas flow path when starting the fuel cell system, increasing the pressure in the fuel gas flow path and reducing the fuel gas leakage in response to subsequent pressure fluctuations. A gas leak judging means for performing a gas leak judging process for judging;
Current detection means for detecting a current flowing between the fuel cell and the voltage converter, or a current flowing through the voltage converter;
A short-circuit fault determination unit that determines that a short-circuit fault has occurred in the voltage converter when the detected current value of the current detection unit or the current-time integrated value based on the detected current value is greater than or equal to a threshold value during the gas leakage determination process; ,
When the short-circuit fault of the voltage conversion device is determined to have occurred by short-circuit failure judging means, the fuel cell system characterized by comprising an informing means for informing the occurrence of a short-circuit failure. The fuel cell system according to claim 1 or 2 ,
A fuel cell system comprising: an operation stop unit that stops a power generation operation of the fuel cell when it is determined by the short circuit failure determination unit that a short circuit failure has occurred in the voltage converter.

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